Recent reports of dead smallmouth bass, catfish and carp on the Susquehanna River are being investigated by the Pennsylvania Fish and Boat Commission.

Although the commission has added an online reporting system for those observing dead fish on the river, to the telephone hotline launched last year, commission biologists believe the fish kills have been caused by spawning-related stress.

"Spawning requires a lot of energy and is very stressful on fish," said Dave Miko, chief of the Commission's Fish Management Division. "With all that energy exerted in egg lying, they have a harder time fighting off infection from a variety of bacteria and viruses."

In addition, he noted, "the rigors of spawning may result in abrasions to snouts, tails and fins during courting, nest preparation and defense. These open sores can become infected and may lead to death."

Miko explained, "Every year, we get these reports, but we are taking special note" because of problems with dying, young smallmouth bass in the river that have caused angler and commission concern since 2005.

The commission has received several reports of fish kills in the river, ranging from 1-30 fish.
River currents can accumulate fish that have died in a larger stretch of the river into smaller pockets and eddies, and that "can give the impression of a larger fish kill in an area" than actually occurred there, said Miko.

However, he added, "we're not taking these lightly. That's why we have the hotlines set up."

In springs with lower water flows and corresponding warmer waters, the kill of bass, catfish and carp might not be so concentrated together, according to Miko. In springs with higher flows and colder temperatures, such as this year, "it stretches out the time" of spawning for all the species and leads to combined fish kills.

Commission biologists currently do not believe the recent fish kills are related to the ongoing problems with young-of-the-year bass in the river, according to Miko.

"At this point we think they are separate issues, however we've collected fish" - pre-spawn, pre-kill reports smallmouth bass - for testing at the Lee town Science Center of the U.S. Geologic Service in Kernersville, W. Va., he explained.

Independent of the fish kills now being reported, the biologists wanted to have the health of those fish investigated to determine if the condition of those adult bass might be leading to weaker eggs and weaker fish hatching from those eggs.

"We're not pinpointing this" as the cause of the ongoing, young-of-the-year problem, Miko cautioned. "It's another avenue of investigation."

The commission, the Pennsylvania Department of Environmental Protection and the USGS again this year have expanded their efforts to investigate the potential causes of the fish kills and disease which have occurred in young smallmouth bass in recent years.

"We are expanding water quality monitoring sites, extending smallmouth bass young of the year disease monitoring into tributaries of the Susquehanna River, and initiating histological and pathological analysis of adult and young of the year smallmouth bass from the Susquehanna River system," said Miko.

Timely reports from anglers and others on the river of the current fish kills are another source of monitoring.

In fish kill investigations, dying but not yet dead fish are the most valuable when trying to determine a cause of death. That's because there are numerous common pathogens that rapidly colonize in a dead fish, making it difficult to determine the cause of death.

"Users of the resource often provide the commission with the first indication that something is occurring along waterways," said Miko.